Fix commit lsn send

[dentiny]

Summary

The bug is:

• On recovery, we send out commit LSN and replication LSN as the latest iceberg snapshot LSN
• But later, we update commit LSN with the commit message we receive (which is the commit message body end LSN)
• It leads to a problem: end LSN could be smaller than our the recovered LSN, which leads to LSN regression
• This PR fixes it by re-using the same strategy as replication LSN, which only updates channel value when a larger LSN is met

Related Issues

Closes #2165

Checklist

• Code builds correctly
• Tests have been added or updated
• Documentation updated if necessary
• I have reviewed my own changes